The animation-timing-functionCSS property sets how an animation progresses through the duration of each cycle.

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It is often convenient to use the shorthand property animation to set all animation properties at once.

Timing functions may be specified on individual keyframes in a @keyframes rule. If no animation-timing-function is specified on a keyframe, the corresponding value of animation-timing-function from the element to which the animation is applied is used for that keyframe.

A keyframe's timing function is applied on a property-by-property basis from the keyframe on which it is specified until the next keyframe specifying that property, or until the end of the animation if there is no subsequent keyframe specifying that property. As a result, an animation-timing-function specified on the 100% or to keyframe will never be used.

Values

The timing function that corresponds to a given animation, as determined by animation-name.

The non-step keyword values (ease, linear, ease-in-out, etc.) each represent cubic Bézier curve with fixed four point values, with the cubic-bezier() function value allowing for a non-predefined value. The step timing functions divides the input time into a specified number of intervals that are equal in length. It is defined by a number of steps and a step position.

ease

Equal to cubic-bezier(0.25, 0.1, 0.25, 1.0), the default value, increases in velocity towards the middle of the animation, slowing back down at the end.

linear

Equal to cubic-bezier(0.0, 0.0, 1.0, 1.0), animates at an even speed.

ease-in

Equal to cubic-bezier(0.42, 0, 1.0, 1.0), starts off slowly, with the speed of the transition of the animating properting increasing until complete.

Equal to cubic-bezier(0.42, 0, 0.58, 1.0), with the animating properties slowly transitioning, speeding up, and then slowing down again.

cubic-bezier(p1, p2, p3, p4)

An author defined cubic-bezier curve, where the p1 and p3 values must be in the range of 0 to 1.

steps(n, <jumpterm>)

Displays an animation iteration along n stops along the transition, displaying each stop for equal lengths of time. For example, if n is 5, there are 5 steps. Whether the animation holds temporarily at 0%, 20%, 40%, 60% and 80%, on the 20%, 40%, 60%, 80% and 100%, or makes 5 stops between the 0% and 100% along the animation, or makes 5 stops including the 0% and 100% marks (on the 0%, 25%, 50%, 75%, and 100%) depends on which of the following jump terms is used:

jump-start

Denotes a left-continuous function, so that the first jump happens when the animation begins;

jump-end

Denotes a right-continuous function, so that the last jump happens when the animation ends;

jump-none

There is no jump on either end. Instead, holding at both the 0% mark and the 100% mark, each for 1/n of the duration.

jump-both

Includes pauses at both the 0% and 100% marks, effectively adding a step during the animation iteration.

start

Same as jump-start.

end

Same as jump-end.

step-start

Equal to steps(1, jump-start)

step-end

Equal to steps(1, jump-end)

Note: When you specify multiple comma-separated values on an animation-* property, they will be assigned to the animations specified in the animation-name property in different ways depending on how many there are. For more information, see Setting multiple animation property values.